make better use of horizontal space in ncls

[dankamongmen]

ncls currently prints everything on different lines, even if it doesn't have an image associated. we ought make more efficient use of available horizontal space. this is trivial for the case without images, but gets more interesting when images are involved. basically, i'd like to see us:

• look like regular ls output when there are no images present, using some columns (or at least multiple filenames per line when possible, if not regular columns), and
• when, for instance, showing the chunli* files from data, put them on the same lines.

this latter case ought pretty much look like @hacker9's lsix, except they render fonts themselves, and we're not going to be doing that.

[dankamongmen]

this is not a duplicate of #2008, but it's similar.